Mashable

The 140-kilometer Berlin Wall was in fact two barriers. The first was constructed rapidly in August 1961. The second, parallel barrier, 100 meters into the Eastern zone, was erected in June 1962.

The area in between the two barriers was known as the Death Strip.

The wall was initially constructed as a wire fence. By its demise in 1989, it consisted of 45,000 sections of reinforced concrete. At key points, the wall was deliberately made weaker so Soviet military vehicles could swiftly break through in a time of war.

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No one has the intention of erecting a wall!

WALTER ULBRICHT, EAST GERMAN HEAD OF STATE, JUNE 1961.

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Image: Patrice Habans/ParisMatch/Scoop

IMAGE: Keystone-France/Gamma-Keystone via Getty Images

IMAGE: Patrice Habans/Paris Match via Getty Images

Image: Keystone France

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East Berlin border guards adding barbed wire to the newly built Berlin Wall.

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July 5, 1962

On Berlin's Bernauer Street, the Volkspolice built a larger wall next to the old one.

Image: Keystone-France

East German workmen reinforce the Berlin Wall by putting glass fragments on top of the brickets.